Electrical device with power quality event protection and associated method

ABSTRACT

An electrical device includes a first terminal structured to electrically connect to a power source; a second terminal structured to electrically connect to a load; a voltage sensor electrically connected to a point between the first and second terminals and being structured to sense a voltage at the point between the first and second terminals; a switch electrically connected between the first terminal and the second terminal; and a control unit structured to detect a power quality event in the power flowing between the first and second terminals based on the sensed voltage and to control a state of the switch based on the detected power quality event.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of, and claims priority to, U.S.patent application Ser. No. 15/979,896, filed May 15, 2018, which is acontinuation of, and claims priority to, U.S. patent application Ser.No. 14/570,036, filed Dec. 15, 2014, entitled “ELECTRICAL DEVICE WITHPOWER QUALITY EVENT PROTECTION AND ASSOCIATED METHOD”, the contents ofwhich are incorporated herein by reference.

BACKGROUND Field

The disclosed concept relates generally to electrical devices, and moreparticularly, to electrical devices that provide protection from powerquality events. The disclosed concept is also related to providingprotection from power quality events.

Background Information

There are various types of power quality events that occur on powerdistribution networks and conductors that can cause damage to loads andassociated power converters. Some examples of such power quality eventsare transients, interruptions, sags, swells, waveform distortions,voltage fluctuation, and frequency variations.

Transients are impulse type overvoltage events, while swells are longerovervoltage events. Both transients and swells can damage a load. Surgeprotection devices are typically used to protect against transients.However, surge protection devices do not protect against swells. Infact, the surge protection device itself may be damaged by swells.

An uninterruptible power supply (UPS) or a power conditioner can limitthe amount of voltage to a load, which offers a degree of protectionfrom swells. A UPS or power conditioner can also protect againstinterruptions and sags. However, a UPS or power conditioner is anexpensive device, and as such, is usually only used for critical loadsthat need continuous power.

There is a need for electrical devices that provide protection frompower quality events. There is also a need for methods of providingprotection from power quality events.

SUMMARY

These needs and others are met by embodiments of the disclosed concept,which are directed to an electrical device including control unit thatis structured to detect a power quality event and to open a switch basedon the detected power quality event.

In accordance with aspects of the disclosed concept, an electricaldevice comprises: a first terminal structured to electrically connect toa power source; a second terminal structured to electrically connect toa load; a voltage sensor electrically connected to a point between thefirst and second terminals and being structured to sense a voltage atthe point between the first and second terminals; a switch electricallyconnected between the first terminal and the second terminal; and acontrol unit structured to detect a power quality event in the powerflowing between the first and second terminals based on the sensedvoltage and to control a state of the switch based on the detected powerquality event.

In accordance with other aspects of the disclosed concept, a method ofproviding protection from power quality events comprises: sensing avoltage at a point between a first terminal electrically connectable toa power source and a second terminal electrically connectable to a load;detecting a power quality event in power flowing between the firstterminal and the second terminal based on the sensed voltage; andopening a switch electrically connected between the first and secondterminals based on the detected power quality event.

In accordance with other aspects of the disclosed concept, an electricaldevice comprises: a first terminal structured to electrically connect toa power source; a second terminal structured to electrically connect toa load; a voltage sensor electrically connected to a point between thefirst and second terminals and being structured to sense a voltage atthe point between the first and second terminals; a buck converterelectrically connected between the first terminal and the secondterminal; and a control unit structured to detect a power quality eventin the power flowing between the first and second terminals based on thesensed voltage and to control a duty cycle of the buck converter basedon the detected power quality event.

BRIEF DESCRIPTION OF THE DRAWINGS

A full understanding of the disclosed concept can be gained from thefollowing description of the preferred embodiments when read inconjunction with the accompanying drawings in which:

FIG. 1 is a schematic diagram of an electrical device including avoltage sensor and control unit in accordance with an example embodimentof the disclosed concept;

FIG. 2 is a schematic diagram of an electrical device including avoltage sensor shown in detail in accordance with an example embodimentof the disclosed concept;

FIGS. 3 and 4 are schematic diagrams of electrical devices includingcapacitors in accordance with example embodiments of the disclosedconcept;

FIGS. 5-7 are schematic diagrams of electrical devices including a buckconverter in accordance with example embodiments of the disclosedconcept; and

FIG. 8 is a schematic diagram of a circuit interrupter including avoltage sensor and control unit in accordance with an example embodimentof the disclosed concept.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Directional phrases used herein, such as, for example, left, right,front, back, top, bottom and derivatives thereof, relate to theorientation of the elements shown in the drawings and are not limitingupon the claims unless expressly recited therein.

As employed herein, the statement that two or more parts are “coupled”together shall mean that the parts are joined together either directlyor joined through one or more intermediate parts.

As employed herein, the term “number” shall mean one or an integergreater than one (i.e., a plurality).

As employed herein, the term “fault condition” shall mean an electricalcurrent based fault that creates a risk of fire or personal shock. Faultconditions may include, without limitation, an overcurrent condition, anarc fault condition, and a ground fault condition. Fault conditions donot include transients, interruptions, sags, swells, waveformdistortions, voltage fluctuations, or frequency variations.

As employed herein, the term “power quality event” shall mean a voltagebased disturbance on the power line (e.g., conductors) that maypotentially cause damage, reduced life, interrupted operation, or lossof data to electrical and electronic devices (i.e., loads) connected tothe power line. Power quality events include, without limitation,transients, interruptions, sags, swells, waveform distortions, voltagefluctuations, and frequency variations.

As employed herein, the term “transients” shall mean voltage impulsescaused by, without limitation, lightning, electrostatic discharge, orswitching of inductive or capacitive loads. A typical voltage impulse isa high voltage (e.g., without limitation, 10 kV) for a short duration(e.g., without limitation, 50 ns).

As employed herein, the term “interruptions” shall mean a loss of power.The loss of power may be due to, without limitation, an open switch, autility failure, or a component failure. In a typical interruption,there is zero voltage for more than one half of a cycle.

As employed herein, the term “sags” shall mean a reduction of thevoltage of the power line. Sags may be due to, without limitation,startup of a load or the presence of a fault. A typical sag is, withoutlimitation, less than 70% of rated voltage for more than one half of acycle, or a sustained undervoltage (e.g., without limitation, less than90% of rated voltage).

As employed herein, the term “swells” shall mean an increase in thevoltage of the power line. Swells may be due to, without limitation,load changes or utility faults. A typical swell is, without limitation,greater than 120% of rated voltage for more than half of a cycle, or asustained overvoltage (e.g., without limitation, greater than 110% ofrated voltage).

As employed herein, the term “waveform distortions” shall mean thepresence of any voltage content outside the fundamental power frequency(i.e., DC, 50 Hz, 60 Hz, etc.). Waveform distortions may include,without limitation, harmonics due to non-linear electronic loads (e.g.,without limitation, power converters), DC offset due to faultyrectifiers, and high frequency noise due to, for example, powerconverter switching.

As employed herein, the term “voltage fluctuations” shall mean a voltagethat varies over time beyond the intended voltage cycles of thefundamental power frequency. Voltage fluctuations may be caused by, forexample, intermittent operation of load equipment. A typical voltagefluctuation is, without limitation, a fluctuation in voltage between 95%and 105% of the rated voltage at a rate of less than 25 Hz.

As employed herein, the term “frequency variations” shall mean afrequency that is not maintained at a constant value (e.g., withoutlimitation, 50 Hz or 60 Hz). Frequency variations may be due to, withoutlimitation, a standby or backup generator that is not governed properly.

FIG. 1 is a schematic diagram of an electrical device 100 in accordancewith an example embodiment of the disclosed concept. The electricaldevice 100 includes a first terminal 102 structured to electricallyconnect to a power source 1 (e.g., without limitation, an AC or DC powersource) and a second terminal 104 structured to electrically connect toa load 2.

The electrical device 100 includes a voltage sensor 106 that iselectrically connected to a point between the first terminal 102 and thesecond terminal 104. The voltage sensor 106 is structured to sense avoltage at the point between the first terminal 102 and the secondterminal 104.

The electrical device 100 also includes a control unit 108. The controlunit 108 is structured to determine if a power quality event occurs inthe power flowing between the first terminal 102 and the second terminal104 based on the voltage sensed by the voltage sensor 106. Power qualityevents include, for example, transients, interruptions, sags, swells,waveform distortions, voltage fluctuations, and frequency variations. Itwill be appreciated that the control unit 108 may be capable ofdetecting one power quality event, a subset of the power quality events,or all of the power quality events without departing from the scope ofthe disclosed concept. For example and without limitation, in oneexample embodiment of the disclosed concept, the control unit 108 iscapable of detecting transients and swells. In another exampleembodiment of the disclosed concept, the control unit 108 is capable ofdetecting transients, interruptions, sags, and swells. In yet anotherexample embodiment of the disclosed concept, the control unit 108 iscapable of detecting transients, interruptions, sags, swells, waveformdistortions, voltage fluctuations, and frequency variations.

The control unit 108 may include a processor and a memory. The processormay be, for example and without limitation, a microprocessor, amicrocontroller, or some other suitable processing device or circuitry,that interfaces with the memory. The memory can be any of one or more ofa variety of types of internal and/or external storage media such as,without limitation, RAM, ROM, EPROM(s), EEPROM(s), FLASH, and the likethat provide a storage register, i.e., a machine readable medium, fordata storage such as in the fashion of an internal storage area of acomputer, and can be volatile memory or nonvolatile memory. It is alsocontemplated that the control unit 108 may be implemented in circuitrywithout the use of a processor or memory.

The electrical device 100 further includes a switch 110 electricallyconnected between the first terminal 102 and the second terminal 104.When the switch 110 is open, the first terminal 102 and the secondterminal 104 are electrically disconnected. When the switch 110 isclosed, the first terminal 102 and the second terminal 104 areelectrically connected. The control unit 108 is structured to controlthe state of the switch 110 based on the detected power quality event.For example and without limitation, the control unit 108 may bestructured to open the switch 110 when a swell is detected and to closethe switch 110 after the swell is completed.

The switch 110 may be any suitable type of electrically controlledswitch. In some example embodiments of the disclosed concept, the switch110 is a solid state switch (e.g., without limitation, a transistor).Solid state switches provide a fast switching time which allow theswitch 110 to open quickly in the case of a power quality event, thusprotecting the load 2 from damage.

Conventional surge protection devices can provide protection againsttransients where the voltage is greater than 140% of nominal voltage forup to 3 ms. However, conventional surge protection devices do notprovide protection against swell of greater than 120% of nominal voltagefor more than 3 ms or greater than 110% of nominal voltage for more than0.5 s. These types of swells are in a range than can cause damage toequipment. The electrical device 100 of FIG. 1 can provide low costprotection from these types of swells by opening the switch 110 when theswell is detected. Although the interruption due to opening the switch110 may be inconvenient in some circumstances, the electrical device 100prevents damage to the load 2.

Referring to FIG. 2, an electrical device 200 in accordance with anexample embodiment of the disclosed concept is shown. The electricaldevice 200 of FIG. 2 is similar to the electrical device 100 of FIG. 1.However, in the electrical device 200 of FIG. 2, a voltage sensor 106′in accordance with an example embodiment of the disclosed concept isshown in more detail.

The voltage sensor 106′ includes a first resistor 112 and secondresistor 114. The first resistor 112 has a first end electricallyconnected to the point between the first terminal 102 and the secondterminal 104 and a second end electrically connected to a first end ofthe second resistor 114. As noted above, the first end of the secondresistor 114 is electrically connected to the second end of the firstresistor 112. A second end of the second resistor 114 is electricallyconnected to a neutral. The second end of the first resistor 112 and thefirst end of the second resistor 114 are electrically connected to thecontrol unit 108 so that the control unit 108 may receive the voltagesensed by the voltage sensor 106′.

FIG. 3 is a schematic diagram of an electrical device 300 in accordancewith another example embodiment of the disclosed concept. The electricaldevice 300 of FIG. 3 is similar to the electrical device 100 of FIG. 1.However, the electrical device 300 of FIG. 3 includes a capacitor 116electrically connected between the switch 110 and the second terminal104 and a DC power source 1′. The capacitor 116 is structured to providepower to the load 2 for a period of time after the switch 110 opens. Thecapacitor 116 allows the load 2 continue operating even if the switch110 is opened briefly due to an interruption or other power qualityevent. In one example embodiment, the capacitor 116 is able to support acurrent of 15 A for 20 ms. However, it is contemplated that any suitablecapacitor 116 may be employed. As previously mentioned, an interruptiondue to opening the switch 110 may be inconvenient. Thus, the addition ofthe capacitor 116 may remove that inconvenience.

FIG. 4 is a schematic diagram of an electrical device 300′ in accordancewith another example embodiment of the disclosed concept. The electricaldevice 300′ of FIG. 4 is similar to the electrical device 300 of FIG. 3.However, the electrical device 300′ of FIG. 4 further includes a secondcapacitor 116′ and switches 117,117′ associated with the capacitors116,116′. The capacitors 116,116′ and switches 117,117′ form a switchedcapacitor circuit. The switches 117,117′ may be controlled by thecontrol unit 108. The switched capacitor circuit facilitates use of theelectronic device 300′ in AC applications. During the positive halfcycle, the switch 117 is closed during increasing voltage and the otherswitch 117′ is open, and during the negative half cycle, the switch 117is open and the other switch 117′ is closed during increasing voltage.This allows the capacitors 116,116′ to charge. When the switch 110 isopened based on a power quality event, the control unit 108 thencontrols switches 117,117′ to open and close at appropriate times todeliver AC power to the load 2. Thus, the electrical device 300 of FIG.3 allows the load 2 to continue operating even if the switch 110 isopened briefly due to an interruption or other power quality event in DCapplications and the electrical device 300′ allows the load 2 tocontinue operating even if the switch 110 is opened briefly due to aninterruption or other power quality event in AC applications.

FIG. 5 is a schematic diagram of an electrical device 400 in accordancewith another example embodiment of the disclosed concept. The electricaldevice 400 of FIG. 5 is similar to the electrical device 100 of FIG. 1.However, the electrical device 400 of FIG. 5 includes a buck converter118 electrically connected between the first terminal 102 and the secondterminal 104. The control unit 108 is structured to control a duty cycleof the buck converter 118 based on the detected power quality event. Forexample and without limitation, when no power quality events aredetected, the control unit 108 may control the buck converter 118 at a100% duty cycle. On the other hand, when a swell is detected, thecontrol unit 108 may reduce the duty cycle of the buck converter 118which lowers the output voltage of the buck converter 118. It iscontemplated that the electrical device 400 of FIG. 5 may reduce theduty cycle of the buck converter 118 in response to swells rather thanopening the switch 110, thus avoiding an interruption of power due toswells. It is also contemplated that the control unit 108 may reduce theduty cycle of the buck converter to 0% in the case that the powerquality event warrants cutting off power to the load 2. It is furthercontemplated that in some embodiments of the disclosed concept, theswitch 110 may be disposed between the buck converter 118 and the secondterminal 104. A buck converter 118′ in accordance with an exampleembodiment of the disclosed concept will be described in more detailwith respect to FIG. 6.

FIG. 6 is a schematic diagram of an electrical device 500 in accordancewith an example embodiment of the disclosed concept. The electricaldevice 500 of FIG. 6 is similar to the electrical device 400 of FIG. 5.However, the electrical device 500 of FIG. 6 includes a buck converter118′ in accordance with an example embodiment of the disclosed conceptshown in more detail.

The buck converter 118′ includes first and second switches 120,121,first and second inductors 122,124, first through fourth diodes126,128,130,132, and a capacitor 134. The first and second switches120,121 are solid state switches (e.g., without limitation,transistors). The first and second switches 120,121 are electricallyconnected to the first terminal 102 and theirs states are controlled bythe control unit 108.

The buck converter 118′ includes parallel branches. The first branchincludes the first switch 120, the first inductor 122, and the first andsecond diodes 126,128. The second branch includes the second switch 121,the second inductor 124, and the third and fourth diodes 130,132. Thecapacitor 134 is common to both branches.

In the first parallel branch, the first diode 126 is electricallyconnected between the first switch 120 and a neutral 136. The firstdiode 126 serves as a flyback to protect the first switch 120 fromextreme voltages when the first switch 120 turns off The first inductor122 and the capacitor 134 act as filters to smooth the flow of currentand the output voltage of the buck converter 118′. When the first switch120 is off, the first inductor 122 draws current from the neutral 136.The current flows through the second diode 128 to the output of the buckconverter 118′ during positive half cycles of an AC cycle when the buckconverter 118′ is electrically connected to an AC power source.

In the second parallel branch, the third diode 130 is electricallyconnected between the second switch 121 and the neutral 136. The thirddiode 130 serves as a flyback to protect the second switch 121 fromextreme voltages when the second switch 121 turns off. The secondinductor 124 and the capacitor 134 act as filters to smooth the flow ofcurrent and the output voltage of the buck converter 118′. When thesecond switch 121 is off, the second inductor 124 draws current from theneutral 136. The current flows through the fourth diode 132 to theoutput of the buck converter 118′ during negative half cycles of an ACcycle when the buck converter 118′ is electrically connected to an ACpower source.

The parallel branches of the buck converter 118′ allow it to efficientlyoperate when electrically connected to an AC power source. However, whenthe buck converter 118′ is electrically connected to a DC power source,some of the components may be omitted. In particular, the second switch121, the second inductor 124, and the third and fourth diodes 130,132(i.e., the second branch) as well as the second diode 128 may be omittedwhen the buck converter 118′ is electrically connected to a DC powersource as the second branch of the buck converter 118′ is not needed.

FIG. 7 is a schematic diagram of an electrical device 400′ in accordancewith an example embodiment of the disclosed concept. The electricaldevice 400′ of FIG. 7 is similar to the electrical device 400 of FIG. 5.However, in the electrical device 400′ of FIG. 7, the switch 110 isomitted. The control unit 108 may reduce the duty cycle of the buckconverter 118 based on power quality events. Furthermore, reducing theduty cycle of the buck converter 118 to 0% cuts off power to the load 2.

FIG. 8 is a schematic diagram of a circuit interrupter 600 in accordancewith an example embodiment of the disclosed concept. The circuitinterrupter 600 includes first and second terminals 102,104, a voltagesensor 106, a control unit 108, and a switch 110 similar to theelectrical device 100 of FIG. 1. However, the circuit interrupterfurther includes separable contacts 138, an operating mechanism 140, anda trip unit 142.

The separable contacts 138 are electrically connected between the firstterminal and second terminals 102,104 and are movable between a closedposition and an open position. When both the separable contacts 138 andthe switch 110 are closed, the first and second terminals 102,104 areelectrically connected. When either of the separable contacts 138 andthe switch 110 are open, the first and second terminals 102,104 areelectrically disconnected. The operating mechanism 140 is a devicestructured to trip open the separable contacts 138.

The trip unit 142 is structured to detect a fault condition based oninput from the current sensor 144 or other sensors. The fault conditionmay include, without limitation, an over current, a short circuit, aground fault, or an arc fault. Based on detection of a fault condition,the trip unit 142 controls the operating mechanism 140 to trip open theseparable contacts 138.

The trip unit 142 may include a processor and memory. The processor maybe, for example and without limitation, a microprocessor, amicrocontroller, or some other suitable processing device or circuitry,that interfaces with the memory. The memory can be any of one or more ofa variety of types of internal and/or external storage media such as,without limitation, RAM, ROM, EPROM(s), EEPROM(s), FLASH, and the likethat provide a storage register, i.e., a machine readable medium, fordata storage such as in the fashion of an internal storage area of acomputer, and can be volatile memory or nonvolatile memory. It is alsocontemplated that the trip unit 142 may be implemented in circuitrywithout the use of a processor or memory. It is also contemplated thatother types of trip mechanisms such as, without limitation, thermal ormagnetic trip mechanisms may be employed in place of or in addition tothe trip unit 142.

By virtue of the separable contacts 138, the operating mechanism 140,and the trip unit 142, the circuit interrupter 600 is able to provideprotection from fault conditions. By virtue of the voltage sensor 106,the control unit 108, and the switch 110, the circuit interrupter 600 isalso able to provide protection from power quality events.

In some embodiments of the disclosed concept, the trip unit 142 does notcontrol the operating mechanism 140 to immediately trip open theseparable contacts 138 upon detection of a fault condition, but ratherwaits a period of time associated with that type of fault conditionbefore controlling the operating mechanism 140 to trip open theseparable contacts 138. Based on the detection of power quality events,the control unit 108 may change the periods of time associated withfault conditions in the trip unit 142. For example and withoutlimitation, when the control unit 108 detects large frequencyfluctuations, it may indicate that the power source is a less reliablesource such as a generator. In response, the control unit 108 may reducethe periods of time associated with fault conditions in the trip unit142 to cause the trip unit 142.

Although the circuit interrupter 600 is disclosed in relation to onephase, it is contemplated that the circuit interrupter 600 may beemployed in relation to multiple phases and separable contacts me beassociated with each phase.

It is contemplated that the disclosed concept may be employed in avariety of types of devices such as, without limitation, circuitbreakers, meters, receptacles, and power strips.

While specific embodiments of the disclosed concept have been describedin detail, it will be appreciated by those skilled in the art thatvarious modifications and alternatives to those details could bedeveloped in light of the overall teachings of the disclosure.Accordingly, the particular arrangements disclosed are meant to beillustrative only and not limiting as to the scope of the disclosedconcept which is to be given the full breadth of the claims appended andany and all equivalents thereof.

What is claimed is:
 1. An electrical device comprising: a first terminalstructured to electrically connect to a power source; a second terminalstructured to electrically connect to a load; a control unit structuredto detect a power quality event in power flowing between the first andsecond terminals; separable contacts electrically connected between thefirst terminal and the second terminal and being moveable between aclosed position and an open position; an operating mechanism structuredto trip open the separable contacts; and a trip unit structured todetect a fault condition based on the power flowing between the firstand second terminals and to control the operating mechanism to trip openthe separable contacts based on the detected fault condition, whereinopening the separable contacts electrically disconnects the first andsecond terminals, wherein the trip unit is structured to wait apredetermined time associated with the detected fault condition afterdetecting the fault condition before controlling the operating mechanismto trip open the separable contacts, and wherein the control unit isstructured to change the predetermined time associated with the detectedfault condition based on the detected power quality event.
 2. Theelectrical device of claim 1, further comprising: a switch electricallyconnected between the first terminal and the second terminal, whereinthe control unit is structured to control a state of the switch based onthe detected power quality event.
 3. The electrical device of claim 2,wherein the control unit is structured to control the switch to openwhen the power quality event is detected and to close after the powerquality event has ended.
 4. The electrical device of claim 2, whereinthe switch is a solid state switch.
 5. The electrical device of claim 2,further comprising: a capacitor electrically connected at a pointbetween the switch and the second terminal, wherein the capacitor isstructured to provide power to the load for a period of time when theswitch is open.
 6. The electrical device of claim 1, wherein theelectrical device is one of a circuit breaker, a meter, a receptacle,and a power strip.
 7. The electrical device of claim 1, wherein thepower quality event includes at least one of a transient, aninterruption, a sag, a swell, a waveform distortion, a voltagefluctuation, and a frequency variation.
 8. The electrical device ofclaim 7, wherein the power quality event includes at least one of atransient and a swell.
 9. The electrical device of claim 7, wherein thepower quality event includes at least one of a transient, aninterruption, a sag, and a swell
 10. The electrical device of claim 1,wherein the fault condition is one of an overcurrent, a short circuit, aground fault, and an arc fault.
 11. The electrical device of claim 1,further comprising: a buck converter electrically connected between thefirst terminal and the second terminal, wherein the control unit isstructured to control a duty cycle of the buck converter based on thedetected power quality event.
 12. The electrical device of claim 11,wherein the power source is an alternating current power source; andwherein the buck converter includes a first branch that is operableduring a positive half cycle of the power source and a second branchthat is operable during a negative half cycle of the power source. 13.The electrical device of claim 1, further comprising: a voltage sensorelectrically connected to a point between the first and second terminalsand being structured to sense a voltage at the point between the firstand second terminals, wherein the control unit is structured to detectthe power quality event based on the sensed voltage.
 14. The electricaldevice of claim 13, wherein the voltage sensor includes a first resistorand a second resistor; wherein the first resistor has a first endelectrically connected to a point between the first and second terminalsand a second end electrically connected to the second resistor; andwherein the second resistors has a first end electrically connected tothe first resistor and a second end electrically connected to a neutral.15. A method of providing protection from power quality events, themethod comprising: detecting a power quality event in power flowingbetween a first terminal electrically connectable to a power source anda second terminal electrically connectable to a load; detecting a faultcondition in the power flowing between the first and second terminals;opening a set of separable contacts electrically connected between thefirst and second terminals based on the detected fault condition;waiting a predetermined time associated with the detected faultcondition after detecting the fault condition before opening theseparable contacts; and changing the predetermined time associated withthe detected fault condition based on the detected power quality event.16. The method of claim 15, further comprising: opening a switchelectrically connected between the first and second terminals based onthe detected power quality event.
 17. The method of claim 16, furthercomprising: closing the switch after the power quality event has ended.18. The method of claim 16, further comprising: providing a capacitorelectrically connected at a point between the switch and the secondterminal, wherein the capacitor is structured to provide power to theload for a period of time when the switch is open.
 19. The method ofclaim 15, further comprising: sensing a voltage at a point between thefirst terminal and the second terminal electrically connectable to aload, wherein detecting the power quality event includes detecting thepower quality event based on the sensed voltage.
 20. The method of claim15, further comprising: providing a buck converter electricallyconnected between the first terminal and the second terminal; andcontrolling a duty cycle of the buck converter based on the detectedpower quality event.